Well, if the aliens exist outside our light hyper-cone (that is, by definitio, any kind of information from them has never reached and will never reach any piece of information we create) then it is the same.

However, if any aliens have lived or will live anywhere in the visible universe, then that is something we could at least in theory confirm our deny at some point, so it is not the same.

It's also important to remember that time is relative - that is, that events in far away places don't happen at a definite time compared to those happening here. That makes their existence different to me than what we normally think of as existence.

Existence has two senses anyway - one is the empirically verifiable bottom of existence that science can work with: this is the one I was referring to.

The other is a philosophical notion of existence that is harder to pin down. In this sense, God may well exist, the nultiverse with many big bangs may be real, infinity may be real etc. But it is impossible right now to make any kind of scientific arguments about these things, so they can only exist outside the realm of science (as we know it today).